There has been increasing demand for hygienic quality in fiber products such as clothing, duvet covers, curtains, towels, wall cloth (wallpaper), etc. In response to this, various fiber products are now treated with antibacterial/antifungal properties-imparting processes. Particularly in recent years, in-hospital infection and the like are considered to be increasing threats to health, and there have been considerable interests in developing antibacterial/antifungal properties-imparting technique for surgical gowns and various other fiber products which are used in medical facilities.
Thus far, fiber products made of synthetic fibers for example, have their antibacterial/antifungal properties imparted commonly by: mixing a chemical agent such as an antibacterial/antifungal agent, with a spinning dope; spinning the dope thereby producing an antibacterial/antifungal fiber; and then making an antibacterial/antifungal yarn/thread by using the fiber individually or by blending it with other fibers, to obtain fiber merchandise which possesses antibacterial/antifungal properties. Another common practice is first manufacturing a fiber whether it is a fiber itself or a fiber product; and then applying chemical agents such as an antibacterial/antifungal agent to the fiber to impart antibacterial/antifungal properties.
A problem, however, with the above-described process of mixing chemical agents such as an antibacterial/antifungal agent with a spinning dope and spinning the dope, is that during the fiber spinning process, the chemical agents, e.g., the antibacterial agent and/or antifungal agent precipitate on nozzle surfaces, causing yarn-making troubles such as frequent breakage of filament.
On the other hand, in the case where chemical agents such as antibacterial/antifungal agents are applied to a fiber, i.e., a fiber or a fiber product, thereby imparting antibacterial/antifungal properties later to the fiber, wash durability is not always adequate. Especially with repeated cycles of industrial laundry in which washing is commonly performed at 60 through 85 degrees Celsius, there has been a problem that these fibers show drastic deterioration in their antibacterial/antifungal properties.
In recent years, there have been proposals for use of pyridine antibacterial/antifungal agents such as zinc pyrithione, for their superior wash durability as disclosed in Patent Literature 1 through 4.
In cases where a pyridine antibacterial/antifungal agent such as zinc pyrithione is applied to fibers to impart antibacterial/antifungal properties to the fibers, a common process is that the antibacterial/antifungal agent in the form of powder is dispersed in a liquid such as water to make a dispersion liquid in which the antibacterial/antifungal agent is dispersed, and then application to the fibers is made in this dispersion liquid because pyridine antibacterial/antifungal agents are barely soluble in solvents such as water.
In performing this process of applying a pyridine antibacterial/antifungal agent to fibers in a dispersion liquid where the agent is dispersed, it is a common practice that a surfactant of various types, such as anionic, cationic and nonionic surfactants, is added in order to maintain a state of stable dispersion of the pyridine antibacterial/antifungal agent in the liquid.
It is also a common practice that when imparting antibacterial/antifungal properties, etc. to fibers by applying an pyridine antibacterial/antifungal agent dispersion liquid to the fibers as described above, various treating agents such as dyes and softeners are used together with the dispersion liquid in which the antibacterial/antifungal agent is dispersed, for a purpose of performing several treatments in a single process.
Here is a problem, however, that if a dispersion liquid which contains a pyridine antibacterial/antifungal agent dispersed therein as described above and an anionic surfactant added thereto is used together with a treating agent containing cations, or if a dispersion liquid containing a cationic surfactant is used together with a treating agent containing anions, then they react chemically with each other to form aggregation, making it impossible to appropriately disperse the pyridine antibacterial/antifungal agent. This means that if an anionic or cationic surfactant is used, types of usable treating agents will be limited, which in turn makes it impossible to use an appropriate treating agent in performing a process. Also, if an antibacterial/antifungal properties-imparting process is performed separately from other processes, then it will lead to an increased number of process steps, resulting in increased cost.
Further, there have been other problems. For example, when a surfactant of various types such as anionic, cationic, nonionic, etc. is added to a dispersion liquid in which a pyridine antibacterial/antifungal agent is dispersed, foaming can occur, making it impossible to appropriately apply pyridine antibacterial/antifungal agent to fibers.